As shown in etymonline's entry, the word "verdure" comes directly from Old French.
It does indeed have an explicit meaning of physical health and vigour - including sexual.
For instance Henry IV, the first Bourbon King, known for his appetite for both garlic and young women was dubbed the "Vert Galant".
And I can't resist to cite a repartee from one of his best friends François de Bassompierre.
The best way to describe their relationship is that the King and the Maréchal used to share both their military and their feminine conquests.
Anyway, the Maréchal, long after the king had been assassinated found himself in prison for 12 years. When he was eventually allowed out (upon the death of Richelieu), his hair had turned so white that a noble woman made him the remark.
His answer was "Madame, je suis comme les poireaux, la teste blanche et la queue verte." I'm like a leek: a white head but a green tail !